The structure of the complex [Rh2(C0)2(pC1)((C6H5)2PCHZP(C6H5)2)2] [BF,] has been determined by X-ray crystallography, verifying that it is an "A-frame" type species. The structural parameters are similar in most aspects to those of the closely related species [Rh2(CO)2(p-S)((C6H5)2PCH2P(C6H5)2)2], with the significant difference that the "active" site, bridging the two metal centers, is more open to attack by small molecules in the present complex. The title complex crystallizes in the space group C,'-Pi from an acetone solution containing as the only anions PF6-and B(C6HS)c. Evidence suggests that the BFanion results from the leaching of boron from the glass by HF. The reduced unit cell has dimensions n = 13.044 (1) A, b = 14.962 (2) A, c = 12.800 (2) A, a = 96.20 (l)', / 3 = 92.56 (l)O, and y = 86.42 (1)' with 2 = 2. On the basis of 5729 unique, observed reflections the structure was refined by full-matrix, least-squares techni ues to agreement (7) and 1.807 (7) A, Rh-C1 = 2.380 (2) and 2.406 (2) A, C-0 = 1.184 (8) and 1.202 (8) A, Rh-Rh = 3.1520 (8) A, C-Rh-C1 = 170.9 (2) and 172.6 (3)O, and Rh-C1-Rh = 82.38 (5)'. indices of R = 0.046 and R, = 0.064. Some relevant metrical parameters are Rh-P(av) = 2.321 (2) w , Rh-C = 1.794 0020-1669/79/1318-2700$01 .OO/O 1 1 reacts reversibly with C02,s and S024,5,8 and undergoes facile reactions with several other small molecules, including NO, N,Ph+, CS,,9 and TCNE.'O The reactions with CO and SO2 contrast the two possible modes of attack of small molecules a X c , Y,, and Z , are the fractional coordinates of the centroid of the rigid group.The rigid group orientation angles 6 , E , and 17 (radians) are the angles by which the rigid body is rotated with respect to a set of axes X, Y , and Z. The origin is the center of the ring; X is parallel to u * , Z is parallel to c, and Y is parallel to the line defined by the intersection of the plane containing a* and b* with the plane containing b and C.amplitudes of vibration of the individual nonhydrogen atoms, and a listing of observed and calculated structure factor amplitudes used in refinement are a~ai1able.l~ Preparation of [Rh2(CO),(p-CI)(DPM)2][BF4]. To a solution of 0.100 g (0.077 mmol) of [Rh,(CO),(p-Cl)(DPM),] [Rh(CO),ClJ in 10 mL of acetone was added 0.017 g (0.150 mmol) of NaBF4. Slow Reaction of [Rh2(p-OH)3($-C5Me5)2]Cl.4H20 in water with hydrogen (90 O C , 1 atm) gives the green tetranuclear dication [Rh4H4(C5Me5)4]2t, 2Y-(Y-= C1-, PF,-, or BF,; 2Y-= PtCl:-). The BF4salt was characterized by X-ray crystallography (tetragonal unit cell with a = 11.763 ( 5 ) 8, and c = 15.522 (6) A, space group la), the structure was solved by Patterson and Fourier techniques and gave a final R of 0.039. The dication contains four rhodium atoms, each bearing a f'-C5Me5ligand, arranged in a distorted tetrahedral manner (D,d symmetry) with two short (2.655 (1) A) and four long (2.829 (1) A) Rh-Rh bonds. The presence of four hydride ligands in the cation has been shown by N M R spectroscopy; they do not take part in any major fluxiona...
